AT514468A1 - High absorbency polysaccharide fiber and its use - Google Patents

Abstract

The present invention relates to a process for producing high-absorbency polysaccharide fibers containing as a fiber-forming substance a mixture of cellulose and a (1 + 3) giucan and the high-absorbency fibers produced therefrom and their use.

Description

Lenzing AG, PL0554

High absorbency polysaccharide fiber and its use

The present invention relates to a novel superabsorbent polysaccharide fiber, its preparation and properties and their use.

State of the art

Nonwovens, or "nonwovens", are porous fabrics made of textile fibers. With regard to the lengths of the fibers used, a distinction is made between nonwoven spunbonded nonwovens which can be obtained by immediate laying down of the fibers after the spinning process and spunbonded nonwovens of fibers with a defined cutting length. These are either dry way, for example by Verdemassen of Kardenbändem, as is the case in the tampon manufacture, or by wet ways, for. B. similar to the papermaking with subsequent solidification produced. In addition to natural fibers such as wool or cotton also find chemical fibers, including polypropylene or polyester use. In the field of absorbent nonwovens products, predominantly cellulosic fibers are used because of their extremely hydrophilic character. Their high absorption capacity is based on the ability of cellulose to form strong hydrogen bonds with water molecules. In addition, these fibers are characterized by complete biodegradability. In addition to cotton and pulp, especially man-made cellulose fibers, so-called cellulose regenerated fibers, such as viscose or lyocell fibers are used, since these natural cellulose fibers such as cotton exceed in terms of purity, softness and absorbent properties in many areas. Viscose and modal methods, for purposes of the present invention, should also be collectively referred to as "xanthogenate method". be referred to, as they always polysaccharides are reacted with CS2 to the corresponding xanthates. Xanthate processes for the production of cellulose fibers have been known to the skilled person for decades.

Lenzing AG, PL0554

Examples of absorbent nonwovens products include wipes and wipes, sanitary products such as tampons or sanitary napkins, sterile drapes or medical wound care products, and cosmetic products such as cleansing pads or napkins. The requirements for these products vary considerably depending on the intended use. Although there are some minimum requirements, especially with regard to fiber elongation and loop strength, to allow easy carding, the demands on the mechanical properties of the fibers are much lower than in the textile sector. Essential tasks of absorbent nonwovens relate to the absorption, transport, distribution, release and / or retention of liquids under the respective conditions of use. To assess these properties, numerous test methods have been established, including the water retention capacity according to DIN 53814, the sinking time, the water holding capacity, suction capacity and suction speed according to Demand Wettability test, thickness swelling and water vapor absorption. The most important requirement for the fibers used in the field of absorbent nonwovens is a high absorption capacity for water or liquids in general, including blood or ham. For its quantification, especially the water retention capacity and the water retention capacity are used.

The water retention capacity, also called swelling value, represents the amount of retained water after wetting and defined Abschleudem based on the dry initial weight of the fibers in percent. It is mainly determined by the supermolecular fiber structure and pore characteristics.

The water holding capacity corresponds to the amount of water that is held by a fiber swab after immersion in water and defined dripping. These are mainly water trapped in the capillary spaces between the fibers. Significant flow rates

Lenzing AG, PL0554 concern the titer, the crimp, the cross-sectional shape and the equipment of the fibers.

The processes known from the literature for the preparation of cellulose erogenerate fibers with high absorbency can be divided into three groups: 1. Physically influencing the fiber structure:

The possibilities for the physical modification of the fiber structure are varied and range from the variation of the composition of the spinning solution and the spinning bath to influencing the extrusion of the thread and the stretching. By special absorption force are characterized hollow fibers, collapsed hollow fiber structures or fibers with multi-limbed, so-called multilobal cross sections out. Hollow fibers can be prepared for example by the addition of sodium carbonate to viscose. Upon contact with the acidic spinning bath, carbon dioxide is released, which swells the fibers and results in the formation of the hollow structure. US4129679 (A) describes fibers made by such a process. A peculiarity of this method is that the inflated fibers collapse and form multi-limbed cross-sections. Further possibilities for producing fibers having a multilobal cross-sectional shape are the spinning of the cellulose solution through spinnerets whose openings have three or more legs, preferably with a length / width ratio of the legs of 2: 1 or more. Such a method is described in W08901062 (A1).

High crimp fibers also have pronounced hydrophilic properties. Influencing the curling of viscose fibers is possible, for example, by using alternative curling modifiers and / or low modifier concentrations which, under certain circumstances, can be reduced to zero, as described in EPO049710 (A1), in combination with modified viscose compositions and spinning conditions.

A disadvantage of these cross-section modified fibers is the significantly reduced processability in the processing steps (e.g., candling). 2. Influence by incorporation of absorbing substances, in particular polymers:

The addition of hydrophilic polymers such as carboxymethylcellulose (US4289824 (A)), alginic acid or its salts (AT402828 (B)), guar gum (WO9855673 (A1)) or copolymers of acrylic and methacrylic acid to the cellulose solution can greatly increase the water absorption capacity of cellulose regenerated fibers , In DE2550345 (AI) mixed fibers of a matrix of regenerated cellulose with high fluid retention capacity by N-vinylamide polymer dispersed in the matrix are described. US3844287 (A) proposes the preparation of superabsorbent mixed fiber material from a cellulosic regenerate matrix containing a polyacrylic acid salt in a uniform distribution. In both cases, the fiber is produced by the viscose process. 3. Chemical modification of the cellulose regenerated fibers or of the cellulose used:

The aim of these methods is to increase the absorbency by chemical reactions carried out directly on the cellulose regenerated fibers or the cellulosic cellulose. Examples are the graft copolymerization of the cellulose with acrylic acid or the carboxymethylation of viscose fibers in the low-substituted range. Such a method is exemplified by JPH0351366 (A).

From an application point of view, the water retention capacity is the most important parameter in the area of absorbent nonwovens, because, in contrast to the water holding capacity, it corresponds more closely to practical conditions. So it is not enough that a tampon or a wound dressing absorbs body fluid only. For the usability is

Lenzing AG, PL0554 it is essential that the absorbed liquid is kept within the fiber material even under the influence of external forces.

The described physical fiber modifications essentially relate to surface properties, for example the cross-sectional shape and the crimp of the fibers, and therefore only cause an increase in the water absorption capacity. The water retention capacity is not or hardly influenced.

By chemical modifications and / or by incorporation of absorbing substances, the water retention capacity of the fibers can be changed, but the introduction of non-cellulosic groups is not unproblematic. Thus, under certain circumstances, the biodegradability may no longer be given in full. This is the case, for example, in the incorporation of copolymers of acrylic and methacrylic acid,

Another disadvantage is the risk of exceeding maximum allowable extract or ash contents. Thus, in the ashing of cellulose fibers containing sodium carboxylate groups, a certain amount of sodium carbonate is always formed. The introduction of charged groups makes it difficult to observe prescribed pH tolerance ranges. Sodium carboxylate group-containing nonwovens, for example, often have a pH which is clearly in the alkaline range.

US 7,000,000 describes fibers obtained by spinning a solution of polysaccharides consisting essentially of hexose repeat units linked via (1-> 3) glycosidic linkages. These polysaccharides can be prepared by contacting an aqueous solution of sucrose with Giucosyltransferase (GtfJ) isolated from Streptococcus salivarius (Simpson et al.

Microbiology, vol 41, pp 1451-1460 (1995)). "Substantially" in this context means that occasionally defects can occur within the polysaccharide chains at which other binding configurations occur. These polysaccharides are to be referred to as "a (1-" 3) -glucan "for purposes of the present invention.

According to US Pat. No. 7,000,000, the a (l- * 3) * glucan is to be derivatized, preferably acetylated. The solvent is preferably an organic acid, an organic halogen compound, a fluorinated alcohol or a mixture of such components. These solvents are expensive and expensive to regenerate. The absorption properties of the fibers made on this catfish are not disclosed by the US 7,000,000.

In summary, it can be stated that processes relating to the chemical modification of the cellulose or cellulose regenerated fibers and the incorporation of highly absorptive substances into the cellulose matrix have not become established. The reasons for this are manifold and are for example due to the fact that the additional effort is too high due to additional process steps, used high-absorbing substances are too expensive or rejected from a physiological and / or toxicological point of view, the desired absorption properties are not achieved or certain minimum mechanical standards, for example, at high levels Filling levels, can not be achieved.

task

The object was compared to this prior art to provide a fiber and a process for their preparation that does not require cross-sectional and chemical modification, and is completely harmless from a physiological and / or toxicological point of view, but still has a significantly increased Water retention has.

Description of the invention

The solution to the above-described object is a process for producing a high-absorbency polysaccharide fiber by a xanthate process, wherein the fiber-forming substance contains a mixture of cellulose and a (1- »3) -glucan. According to the invention, this is achieved by adding to the cellulose xanthate solution an a (1-> 3) -glucan-containing sodium hydroxide solution. The addition of this glucan solution can take place at various points in the process. Such a polysaccharide

Lenzing AG, PL0554

Fiber is also to be referred to as Vlscose or Modal fiber for the purposes of the present invention, although it contains, in addition to cellulose, another fiber-forming polysaccharide, namely α (1-> 3) -glucan. For the purposes of the present invention The invention is intended to include the term "fiber 4" both staple fibers with a defined cut length and endless filaments. All principles of the invention described below apply in principle both to staple fibers and to continuous filaments.

The particle fiber titer of the fibers according to the invention can be between 0.1 and 10 dtex. It is preferably between 0.5 and 6.5 dtex and more preferably between 0.9 and 6.0 dtex. In the case of staple fibers, the cut length is usually between 0.5 and 120 mm, preferably between 20 and 70 mm and particularly preferably between 35 and 60 mm. In the case of continuous filaments, the number of individual filaments in the filament yarn is between 50 and 10,000, preferably between 50 and 3,000.

The <x (1-> 3) -Guucan can be prepared by adding an aqueous solution. of sucrose with glucosyltransferase (GtfJ) isolated from Streptococcus salivarius (Simpson et al, Microbiology, vol 41, pp 1451-1460 (1995), US 7,000,000).

In a preferred embodiment of the process of the invention, at least 90% of the a (1-> 3) -glucan consists of hexose units and at least 50% of the hexose units are linked by a (1-> 3) -glycosylic bonds.

The process for producing the fiber according to the invention consists in principle of the following essential steps: 1.a. Preparation of alkali cellulose and its xanthogenation 1. b. Preparation of an alkaline glucan solution 2. Mixture of the two solutions 3. Spinning out the α (1-> 3) glucan-containing spinning solution through a nozzle into a sulfuric spinning bath, drawing the fibers and after-treatment.

The total concentration of the fiber-forming substance in the spinning solution may be between 4 and 15 wt .-%, preferably 5.5 to 12 wt .-%.

The fiber-forming substance in the process according to the invention may contain between 1 and 99% by weight of a (1- »3) -glucan. Most preferably, a portion of the a (1-> 3) -glucan is between 5 and 45 weight percent. Below 5%, the effect of the a (1- »3) glucan additive is too low for conventional applications of the fibers according to the invention; Above 45%, competitive reactions around the CS2 in the spinning solutions become too great and the spinnability of the solution drops significantly. However, both limits can be exceeded under special conditions or for special applications of the fibers according to the invention; Also, fibers having an a (1- »3) * glucan content of between 1 and 5% by weight and between 45 and 99% by weight are expressly included in the scope of the present invention.

The remaining portion of the fiber-forming substance preferably consists essentially of cellulose. "Substantially" in this context means that small amounts of other substances can be contained, which mainly come from the cellulosic raw material, generally the pulp. Such other substances are mainly hemlcellulose and other saccharides, lignin residues or the like. They are also contained in commercially available viscose and modal fibers.

However, the scope of the present invention is expressly intended to include those fibers which, in addition to the components mentioned so far, also contain other polysaccharides or functional additives, as are well known in the nonwovens and textile industries.

Lenzing AG, PL0554

The degree of polymerization of the ot (1-> 3) glucan used in the method of the invention, expressed as weight average DPW, can be between 200 and 2000; preferred are values between S00 and 1000,

The present invention also provides a high-absorbency polysaccharide fiber prepared by a xanthate process containing cellulose and a (1-> 3) -glucan. The fiber-forming substance of the fiber according to the invention contains between 1 and 99% by weight, preferably between 5 and 45% by weight of a (1-> 3) -glucan

In a preferred embodiment, the a (1-> 3) -glucan of the polysaccharide fiber of the invention is at least 90% hexose units and at least 50% of the hexose units are linked by a (1- + 3) glycoside linkages , Surprisingly, it has been found that the fiber according to the invention has an extraordinarily high water retention capacity of at least 90%. Depending on the composition and method of production, the water retention capacity is even greater than 100%.

Likewise provided by the present invention is the use of the fibers according to the invention for the production of a wide variety of dry and wet laid papers, nonwovens, hygiene articles such as tampons, panty liners and diapers and other nonwovens, in particular absorbent nonwovens products, but also of textile products such as yarns, fabrics , Crocheted or knitted.

In the following the invention will be described by way of examples. However, the invention is expressly not limited to these examples, but includes all other embodiments based on the same inventive concept.

Examples

The degree of polymerization of the a (1- * 3) -glucans was determined by GPC in DMAc / LiCl. In the following, the weight average of the degree of polymerization (DPW) is always stated.

Example 1)

An aqueous Viskosexanthogenat solution containing 29.8 wt .-% cellulose, 14.9 wt .-% NaOH and 8 wt .-% sulfur, in a dissolving unit with a Löselauge 1 containing 4.5 wt .-% NaOH and then with a Löselauge 2 containing 9 wt. »% a (1-» 3) -glucan and 4.5 wt .-% NaOH and finally reacted with water. The viscose thus prepared contained 8.90% by weight of fiber-forming material, 5.20% by weight of NaOH, and 2.4% by weight of sulfur (for 100% cellulose as the fiber-forming material) having a ripeness index of 14 Hottenroth and a Falling ball viscosity of 80 seconds (determined according to the Zellcheming leaflet III / 5 / E). Viscose solutions were prepared with 10 and 25% ct (1- »3) -glucan. Glucan levels refer to the proportion of a (1-> 3) -glucan on the fiber-forming substance. These viscose contain 2.2 wt .-% sulfur (10% glucan and 90% cellulose as a fiber-forming material) or 1.8 wt .-% sulfur (25% glucan and 75% cellulose as a fiber-forming material). The solution was spun by means of a spinneret into a regenerating bath containing 100 g / l of sulfuric acid, 330 g / l of sodium sulfate and 15 g / l of zinc sulfate. The spinneret had 1053 holes of 50pm diameter. To the viscose spinning solution was added 0.5% by weight of a nitrogen-containing auxiliary. To achieve a corresponding fiber strength, a draw in the secondary bath (92 C, 15 g / 1 H2S04) of about 75%. The take-off speed is 50 m / min. In Comparative Example 1, the viscose of Example 1 was spun into fibers without addition of the glucan-NaOH solution but under otherwise identical conditions as in Example 1,

The properties of the obtained fibers are given in Table 1:

Lenzing AG, PL0554 Example 2:

A viscose containing 8.70% by weight of cellulose, 5.20% by weight of NaOH and 2.3% by weight of sulfur, having a ripeness index of 15% Hottenroth and a falling ball viscosity of 75 seconds (determined according to the Zellcheml-Merkblatt III / 5 / E) was spun by means of a spinneret into a regenerating bath containing 100 g / l sulfuric acid, 310 g / l sodium sulfate and 15 g / l zinc sulfate. The spinneret had 1053 holes of 50 pm diameter. To the viscose spinning solution was added 0.5% by weight of a nitrogen containing auxiliary. To achieve a corresponding fiber strength, a draw in the secondary bath (92 C, 15 g / 1 H2S04) of about 75%. The take-off speed is 50 m / min.

To the viscose solution was added in front of the spinneret, by means of a positive pump, appropriate amounts of aqueous a (1- »3) -glucan-NaOH solution (5 wt% NaOH, 8 wt% a (1-> 3) -glucan ) were added so that fibers with 10.15 and 30% glucan could be produced. These amounts of glucan refer to the proportion of a (1-> 3) -glucan on the entire fiber-forming substance of the polysaccharide fibers.

In a comparative example 2, the viscose from example 2 was spun into fibers without addition of the glucan-NaOH solution, but under otherwise identical conditions as in example 2.

The properties of the resulting fibers are given in Table 1:

I

Table 1

FFk fiber strength conditioned 5 FDk fiber elongation conditioned WRV water retention capacity

Claims (12)

Lenzing AG, PL0554 Claims 1. A process for producing a highly absorbent polysaccharide fiber according to a xanthate process, characterized in that the fiber-forming substance contains a mixture of cellulose and a (1 → 3) glucan. 2. Process according to claim 1, wherein the fiber-forming substance contains between 1 and 99% by weight, preferably between 5 and 45% by weight of a (1- »3) -glucan. 3. The method of claim 1, wherein the method is a viscose method. The process of claim 1 wherein the at (90) -glucan consists of at least 90% hexose units and at least 50% of the hexose units are linked by a (1n> 3) glycosidic linkages. A method according to the preceding claims, wherein the fiber is a staple fiber or an endless filament. 6. High-absorbency polysaccharide fiber produced by a xanthate method, characterized in that it contains cellulose and a (1-> 3) -glucan as the fiber-forming substance. A fiber according to claim 6, wherein the fiber-forming substance contains between 1 and 99% by weight, preferably between 5 and 46% by weight of a (1- »3) -glucan. A fiber according to claim 6, wherein the a (1-> 3) -glucan consists of at least 90% hexose units and at least 50% of the hexose units are linked by a (1-> 3) -glycosidic bonds , A fiber according to claim 6, wherein the fiber has a water retention capacity of at least 90%, preferably greater than 100%. A fiber according to any one of the preceding claims, wherein the fiber is a staple fiber or a continuous filament. 11. Use of the fiber according to claim 6 for the production of nonwovens, hygiene articles, in particular tampons, panty liners and diapers and other absorbent nonwovens products and papers. 12. Use of the fiber according to claim 6 for the production of textile products such as yarns, fabrics, crocheted or knitted fabrics.